I thought I was done crying for the main manga last night but here I am.
A lot of people may think about this being healthy or unhealthy but I think this should be considered normal. Longing is a human nature. Longing for someone that "gave her life to you" for you tu be happy is sooo deep and so relatable even when you didn't experience it first hand.
She seems happy. It seems like she needed to fulfill her and Kaori's last wish before really trying to move on. We all know it was a deep wish to have engagement ring, a wish Kaori couldn't afford to say in her situation. I'm sure Shizuku will start moving on from now on. Even if it slowly.
I like this ending better than just finishing with the other one. Thank you for making me cry a final time for them. I love you author, stay healthy.